Does altitude affect AFUE? or just the input/output BTUs? - Home Energy Pros2017-08-18T05:10:01Zhttp://homeenergypros.lbl.gov/forum/topics/does-altitude-affect-afue-or-just-the-input-output-btus?commentId=6069565%3AComment%3A157812&xg_source=activity&feed=yes&xn_auth=noDale and I are referring to h…tag:homeenergypros.lbl.gov,2015-07-15:6069565:Comment:1844682015-07-15T21:04:10.535ZMorgan M Audetathttp://homeenergypros.lbl.gov/profile/MorganMAudetat
<p>Dale and I are referring to high efficiency condensing boilers designed to recover the latent heat of vaporization in a secondary heat exchanger designed for acidic condensate and capable of the highest combustion efficiency available in a gas-fired appliance. </p>
<p>Dale and I are referring to high efficiency condensing boilers designed to recover the latent heat of vaporization in a secondary heat exchanger designed for acidic condensate and capable of the highest combustion efficiency available in a gas-fired appliance. </p> Now you're just showing off :…tag:homeenergypros.lbl.gov,2015-07-15:6069565:Comment:1844672015-07-15T20:59:16.676ZMorgan M Audetathttp://homeenergypros.lbl.gov/profile/MorganMAudetat
<p>Now you're just showing off :-). </p>
<p>Now you're just showing off :-). </p> Yes,
They were trying to crea…tag:homeenergypros.lbl.gov,2015-07-15:6069565:Comment:1845512015-07-15T16:56:22.736ZDale Pickardhttp://homeenergypros.lbl.gov/profile/DalePickard
<p>Yes,</p>
<p>They were trying to create a combustion system that could calibrate itself to the gas it it's burning and the air that it's supplied with. What interesting is how the addition of computer tech, software, and new hardware can simplify the electro/mechanical parts of the boiler while adding these performance features at the same time. i.e. The new system uses a very simple, DC proportional gas valve in place of the relatively clunky "negative pressure" gas valve system used in the…</p>
<p>Yes,</p>
<p>They were trying to create a combustion system that could calibrate itself to the gas it it's burning and the air that it's supplied with. What interesting is how the addition of computer tech, software, and new hardware can simplify the electro/mechanical parts of the boiler while adding these performance features at the same time. i.e. The new system uses a very simple, DC proportional gas valve in place of the relatively clunky "negative pressure" gas valve system used in the older boilers, (and all of the competitive boilers). The difference in complexity is visually striking, even to an untrained eye.</p>
<p>As far as plug and play goes.......so far so good, we have a growing number of these in the field - we're hoping in the long term they solve the issues we have seen with propane and altitude.</p> Dale, thanks for the info abo…tag:homeenergypros.lbl.gov,2015-07-15:6069565:Comment:1844622015-07-15T15:18:43.391ZRodney Foxhttp://homeenergypros.lbl.gov/profile/RodFox
<p>Dale, thanks for the info about "lambda sensor-free" burn calibration. This was news to me, and after researching it a while, this seems to be the way to go for a "plug-and-play" sort of combustion appliance for all altitudes.</p>
<p>Dale, thanks for the info about "lambda sensor-free" burn calibration. This was news to me, and after researching it a while, this seems to be the way to go for a "plug-and-play" sort of combustion appliance for all altitudes.</p> Morgan, I got this below from…tag:homeenergypros.lbl.gov,2015-07-04:6069565:Comment:1841342015-07-04T18:29:21.790ZDale Pickardhttp://homeenergypros.lbl.gov/profile/DalePickard
<p>Morgan, I got this below from the Knight installation manual. I note a few things,</p>
<p>-These recommendations are not the "4% for every 1000 ft above 2000 ft" appropriate for natural draft boilers.</p>
<p>-They do indicate will derate itself 4% for every 1000 ft above sea level up to 4500 ft - they just say it occurs without "adjustment". I think this is some pretty squirrely language. It appears that one must derate this equipment even more than natural draft equipment.</p>
<p>-A special…</p>
<p>Morgan, I got this below from the Knight installation manual. I note a few things,</p>
<p>-These recommendations are not the "4% for every 1000 ft above 2000 ft" appropriate for natural draft boilers.</p>
<p>-They do indicate will derate itself 4% for every 1000 ft above sea level up to 4500 ft - they just say it occurs without "adjustment". I think this is some pretty squirrely language. It appears that one must derate this equipment even more than natural draft equipment.</p>
<p>-A special model of this boiler is available for elevations above 3500 ft. (different draft fan?)</p>
<p>-The Knight calls for derating based on flue length as well.</p>
<p>-I think this boiler model uses the Gionnani HX style.</p>
<p>I gather from this that the ability of this class of equipment to adapt to altitude is limited by the capacity of the draft fan and the capacity and pressure drop across the heat exchanger on the gas side - just because the fan is big doesn't mean the heat gets exchanged.</p>
<blockquote><p>Standard Knight wall mount boilers are equipped to operate<br/> from sea level to 4,500 feet only with no adjustments. The boiler will de-rate by 4% for each 1,000 feet above sea level up to 4,500 feet.<br/> 6. High altitude Knight wall mount boilers are equipped to operate from 3,000 to 12,000 feet only with no field adjustments. The boiler will de-rate by 2% for each 1,000 feet above 3,000 feet. High altitude models are manufacturedwith a different control module for altitude operation, but the operation given in this manual remains the same as the standard boilers. A high altitude label (as shown in FIG. A) is also affixed to the unit.</p>
<p>7. The Knight Wall Mount boiler input rate, on some models, is reduced for vent lengths beyond the minimum. Models WB(N,L)081 and WB(N,L)106 with 2" vent will reduce 1% for every 10 feet of vent. Models WB(N,L)151 and WB(N,L)211 with 3" vent will reduce 0.5% for every 10 feet of vent.<br/> 8. Ratings have been confirmed by the Hydronics Section of<br/> AHRI.</p>
</blockquote> Hans,
The car manufacturer's…tag:homeenergypros.lbl.gov,2015-07-04:6069565:Comment:1842132015-07-04T04:34:19.839ZDale Pickardhttp://homeenergypros.lbl.gov/profile/DalePickard
<p>Hans,</p>
<p>The car manufacturer's are doing it with mass flow sensors and oxygen sensors "lamda" sensors to operate the fuel injection and gas air mix, even dynamically as the car gains altitude.</p>
<p>Gas fuels are different from liquid or even solid fuels where it's common to use "lamda" sensors to indicate oxygen content of the air. (I understand these sensors are expensive and subject to failure) What Viessmann has done is to use the strength of the ionization current produced in the…</p>
<p>Hans,</p>
<p>The car manufacturer's are doing it with mass flow sensors and oxygen sensors "lamda" sensors to operate the fuel injection and gas air mix, even dynamically as the car gains altitude.</p>
<p>Gas fuels are different from liquid or even solid fuels where it's common to use "lamda" sensors to indicate oxygen content of the air. (I understand these sensors are expensive and subject to failure) What Viessmann has done is to use the strength of the ionization current produced in the flame as control point to regulate the gas and air supply to produce a clean burn even under modulation at high altitude. The boiler controls regularly self calibrate the burner for the location that the boiler is in.</p> I was trying to avoid naming…tag:homeenergypros.lbl.gov,2015-07-04:6069565:Comment:1842122015-07-04T04:22:43.808ZDale Pickardhttp://homeenergypros.lbl.gov/profile/DalePickard
<p>I was trying to avoid naming manufacturers, but I was going by the published information for the smaller Knight boilers which use the "fire tube hx". Check me but I understood there was a derating schedule for these boilers.</p>
<p>Also note, the technology that Viessmann promotes as "Lamda" is used otherwise with oxygen sensors as per the automotive market. I understand that VM's use of the ionization current as an indicator of combustion quality is unique. The simple proportional gas valve…</p>
<p>I was trying to avoid naming manufacturers, but I was going by the published information for the smaller Knight boilers which use the "fire tube hx". Check me but I understood there was a derating schedule for these boilers.</p>
<p>Also note, the technology that Viessmann promotes as "Lamda" is used otherwise with oxygen sensors as per the automotive market. I understand that VM's use of the ionization current as an indicator of combustion quality is unique. The simple proportional gas valve is much simpler then the "negative pressure" system used in the older VM equipment and in newer equipment by other manufacturers.</p>
<p>What you said about "power companies derate the gas at high altitude is simply to anticipate gas appliances tuned for low sea level" makes sense and answers my questions - I didn't understand why the gas itself would be of lower energy content. However, if one derates the gas and you derate the equipment then we get a double whammy when it comes to sizing even atmospheric equipment.</p> I look at this not about AFUE…tag:homeenergypros.lbl.gov,2015-07-04:6069565:Comment:1839432015-07-04T01:47:21.505ZEric Kjelshushttp://homeenergypros.lbl.gov/profile/EricKjelshus
<p>I look at this not about AFUE, but flue gas dewpoint. If your burn rate is rotting the heat exchanger then you have short life of heating system. Old school is about dewpoint - if natural gas flue products are at 130'F @ 9% CO2 or 113'F @ 4.5% CO2. Propane Flue Products are at 122' F @10% CO2 or 103'F @5% CO2. % of heat contained in water vaporization 10% natural gas - 93 lbs of water = 10 gallons of water. 10 hour of run time for natural gas can be gallons of water that must…</p>
<p>I look at this not about AFUE, but flue gas dewpoint. If your burn rate is rotting the heat exchanger then you have short life of heating system. Old school is about dewpoint - if natural gas flue products are at 130'F @ 9% CO2 or 113'F @ 4.5% CO2. Propane Flue Products are at 122' F @10% CO2 or 103'F @5% CO2. % of heat contained in water vaporization 10% natural gas - 93 lbs of water = 10 gallons of water. 10 hour of run time for natural gas can be gallons of water that must be removed from the flue. This is the ratio of hydrogen to carbon - the highest is rate is with natural gas. The new flue gas meters read this but you have to use it. </p>
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<p>Last winter I was at a Nat gas up flow with rated AFUE of 92.3% but my Meter reads 98.5% this was over rated with low air flow with dirty filter and coils with dog hair/fiber glass/sheet rock dust/saw dust, cold inside On side of furnace is rated at .5 SP but this was 1.2 in water. Flue temp was 135' and supply was 147' or a spit of 88' on side says max of 45'. IT ALL ABOUT AIR FLOW. This furnace lasted 2 mo as a new work heater. The safety are jumped to make it run this bad.</p>
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<p>how do you derate a furnace? - if air flow is right its just gas presser and BTU's in gas</p>
<p> </p> Though Viessmann is relativel…tag:homeenergypros.lbl.gov,2015-07-03:6069565:Comment:1840332015-07-03T22:45:12.289ZMorgan M Audetathttp://homeenergypros.lbl.gov/profile/MorganMAudetat
<p>Though Viessmann is relatively unique in the application of Lambda technology to residential condensing boilers, most condensing boilers (I have installed 12 manufacturers) burning natural gas will not have to adjusted for altitude up to 6,000 feet or so. Modulating fans and power burners make for a super-charged performance. </p>
<p>We had many of the old GlowCore boilers on gas wells with zero gas pressure, the boiler literally pulling the gas out of the ground, mixing it with air and…</p>
<p>Though Viessmann is relatively unique in the application of Lambda technology to residential condensing boilers, most condensing boilers (I have installed 12 manufacturers) burning natural gas will not have to adjusted for altitude up to 6,000 feet or so. Modulating fans and power burners make for a super-charged performance. </p>
<p>We had many of the old GlowCore boilers on gas wells with zero gas pressure, the boiler literally pulling the gas out of the ground, mixing it with air and burning the mix...always seeking that illusive Stoichiometric combustion nirvana :-). </p>
<p>The reason the power companies derate the gas at high altitude is simply to anticipate gas appliances tuned for low sea level. The efficiency is not de-rated, rather the output, due to the lack of oxygen. If you have a blower you should not have a lack of oxygen or a change in output. </p>
<p>When the gas in Albuquerque is de-rated and the output of a naturally aspirated gas appliance is de-rated as well. A properly tuned, or self-tuning appliance, will not have to be de-rated, the output remaining as listed by the manufacturer. </p>
<p>AFUE is a number proffered by the government to attempt to create a level playing field, much like MPG for cars. Unlike cars, the AFUE is dependent on the proper application, installation, operation and maintenance of the equipment, so that the difference between a condensing boiler claiming 90 vs. 96% thermal efficiency is of little value. </p>
<p>The only significant distinction in real efficiency is properly reflected when the 85% AFUE claimed by some atmospheric appliance manufacturers reflecting the theoretical limit of non-condensing technology. </p>
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<p></p> The heat exchanger gets burnt…tag:homeenergypros.lbl.gov,2015-07-03:6069565:Comment:1841262015-07-03T04:29:42.727ZEric Kjelshushttp://homeenergypros.lbl.gov/profile/EricKjelshus
<p>The heat exchanger gets burnt out, if presser is to high or if mix is to rich, then I see holes in the heat exchanger. I have done gas wells with low and high BTU content and have to test each one with 55 gal of Nat gas with some presser. At the furnace All I can change is gas presser, and some times if all burners get gas.</p>
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<p>The heat exchanger gets burnt out, if presser is to high or if mix is to rich, then I see holes in the heat exchanger. I have done gas wells with low and high BTU content and have to test each one with 55 gal of Nat gas with some presser. At the furnace All I can change is gas presser, and some times if all burners get gas.</p>
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